The present invention relates to a portable telephone and electronic equipment for performing signal transmission by optical signals.
Conventionally, as shown in FIG. 17, there has been a portable telephone which has a first casing 1 having a display panel, and a second casing 2 having an operation panel (see JP 2001-119460 A). The first casing 1 and the second casing 2 are coupled to each other so as to be foldable or developable.
As shown in FIGS. 18A and 18B, the first casing 1 and the second casing 2 are coupled to each other with flexible cables 6 to fulfill signal transmission by electric signals. In more detail, circuit boards 4, 5 are provided in the first casing 1 and the second casing 2, respectively. The circuit board 4 of the first casing 1 and the circuit board 5 of the second casing 2 are coupled to each other with the flexible cables 6. The flexible cables 6 and the circuit boards 4, 5 are connected to each by connectors 7, 8, respectively.
In such transmission of electric signals, generally, electromagnetic-wave noise that occurs from the flexible cables 6 increases in level with increasing signal transmission speed, giving rise to a need for shielding the flexible cables 6.
Therefore, in a conventional portable telephone, a coaxial type flexible cables as shown in FIG. 19 is used as the flexible cables, by which the flexible cable 6 is shielded.
In more detail, the flexible cable 6 has a spacer portion 13 with an internal conductor pattern 12 contained at its center, a base 14 and an inner-side upper cover lay 15 between which the spacer portion 13 is sandwiched from above and below, and a top cover lay 16 and a bottom cover lay 17 with which the base 14 and the upper cover lay 15 are covered from above and below, respectively.
The base 14 has a strip pattern 14a at a center of a bottom surface, and a signal-transmission pattern 14b on both sides of the top surface. The upper cover lay 15 has a strip pattern 15a at a center of the top surface. The top cover lay 16 covers the strip pattern 15a. The bottom cover lay 17 covers the strip pattern 14a. 
In the upper cover lay 15 and the base 14, through holes 22 are formed so as to extend through the upper cover lay 15 and the base 14. With these through holes 22, the strip pattern 15a and the strip pattern 14a are electrically connected to each other.
The internal conductor pattern 12 forms an internal conductor. The strip patterns 15a, 14a and the through holes 22 form external conductors.
Then, even if a high-speed signal is transmitted to the internal conductor pattern 12, the flexible cable 6, which is of a coaxial structure, inhibits electromagnetic waves from leaking to the outside from the flexible cable 6.
However, in this conventional portable telephone, for example, treating high-definition dynamic images involves higher-speed transmission of signals, so that the occurrence of electromagnetic-wave noise comes to matter with increasing transmission speed. Further, countermeasures against electromagnetic waves by the shielding of the flexible cable would cause the complexing of the structure as well as the increasing of size, which matters in uses with limited spaces such as in portable telephones.